Question

I’m trying to build my NSDictionnary to send to a request using the AFNetworking framework, but it seems that I’m quite confused about how to do it properly.

Here’s what the server is expecting :

{
    "limit":10,
    "filters":
    [
        {"field":"owner","operator":"EQUAL","value":"ownerId","type":"integer"},
        {"field":"date","operator":"GE","value":"30 Jun 2010 00:00:00","type":"date"},
    ],
    "order":[{"field":"date","order":"ASC"}],
    "page":0
}

What I’m trying to do (I don’t really know if it’s the right way to do it tbh), is to build a NSDictionary like the following :

NSDictionary *parameters = [NSDictionary dictionaryWithObjectsAndKeys:
                                @"10", @"chunkSize", 
                                [NSDictionary dictionaryWithObjectsAndKeys:
                                    [NSDictionary dictionaryWithObjectsAndKeys:@"owner", @"field", @"EQUAL", @"operator", @"ownerId", @"value", @"integer", @"type", nil],
                                    [NSDictionary dictionaryWithObjectsAndKeys:@"date", @"field", @"GE", @"operator", @"30 Jun 2010 00:00:00", @"value", @"date", @"type", nil],
                                    nil], @"filters",
                                [NSDictionary dictionaryWithObjectsAndKeys:
                                    [NSDictionary dictionaryWithObjectsAndKeys:@"date", @"field", @"ASC", @"order", nil],
                                    nil], @"order",
                                @"0", @"page",
                                nil];

But I have the following error when the view is loading :

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', 
reason: '+[NSDictionary dictionaryWithObjectsAndKeys:]: second object of each pair must be non-nil

I know I screw up building the parameters properly, but I can’t manage to do it after several tries. Could anyone help ? Moreover, I don’t really know the differences that I must implement here with the [] and the {}. I read that {} was for a dictionary and [] for an array, but I don’t really see how to translate it in my case.

Answer 1

Your mistake is that the value for the dictionary starting on line 3 needs to be wrapped in an array.

At least until Objective-C array and hash literals go mainstream, my preferred method for creating complex dictionaries is to build them from an NSMutableDictionary. In your case:

NSMutableDictionary *mutableParameters = [NSMutableDictionary dictionary];
[mutableParameters setValue:@"10" forKey:@"limit"];
// ...

NSMutableArray *mutableFilters = [NSMutableArray array];
NSMutableDictionary *mutableOwnerFilterDictionary = [NSMutableDictionary dictionary];
[mutableOwnerFilterDictionary setValue:@"owner" forKey:@"field"];
// ...
[mutableFilters addObject:mutableOwnerFilterDictionary]; 

[mutableParameters setValue:mutableFilters forKey:@"filters"];
// ...

Also, be sure you’re sending that over as JSON by setting AFJSONParameterEncoding to your AFHTTPClient.